Multiple patterning technologies include lithography-etch/lithography-etch (LELE), self-aligned double patterning (SADP), self-aligned quadruple patterning (SAQP), directed self-assembly (DSA), etc. In SADP and SAQP, masks, such as cut masks or block masks, are applied to generate line ends. For simplicity, the focus in this disclosure is on cut masks, but the masks can be cut masks and/or block masks. SADP and SAQP are preferred solutions for advanced metal routing because there is no overlay error generated compared to LELE.
Electronic design automation (EDA) routing tools generate designs of metal lines to connect cells within an integrated circuit, forming a metal routing layer. The routing tools use metal line design rule checks to ensure that the metal routing layer does not violate any design rules.
Challenges exist in using SADP and/or SAQP for forming the metal routing layer. A separate post-routing decomposition tool is required to generate the cut mask for generating the ends of the continuous metal lines. That is, the routing tool is not aware of mask design rules for forming the cut mask. Typically, there are design rule check errors associated with the cut mask, which requires repeating the routing process. Such an iterative process delays design closure. Further, it is not intuitive to modify metal lines according to cut mask design rule errors. Further, because routing tools are not aware of the cut mask required to form the metal routing layer, the routing tools typically generate metal routing layers that require complex mask geometries that are prohibitively complex for manufacturing. Thus, additional post-routing tools are required to optimize the cut mask, which requires extending the designed metal lines of the metal routing layer to reduce the complexity of the mask geometries as well as adding dummy metal fill extensively, both of which are not included within the designed route timing closure.
A need, therefore, exists for cut-mask-aware routing in designing a metal routing layer, and the resulting devices formed based on the cut-mask-aware routing.